This application claims the priority of 198 26 175.6, filed Jun. 13, 1998, the disclosures of which is expressly incorporated by reference herein.
The invention relates to a method and a system for influencing possible structure-borne sound conductions and possible noise radiations of objects which have at least two at least indirectly mutually adjoining and mutually connected components, a spacer body being arranged in the area of the at least indirect mutual adjoiningxe2x80x94in the following, simplified as xe2x80x9ccontact areaxe2x80x9d.
Examples of such objects are bodies of motor vehicles, such as passenger cars and trucks, airplanes or train cars and the like, casings of machines, internal-combustion engines, machine or engine parts, or machine or motor components, but also framed glass, such as window panes arranged in window frames.
A method for suppressing vibrations introduced into the vehicle body and a corresponding vehicle are known from U.S. Pat. No. 5,332,061. The concerned introduced vibrations originate from the engine and are transmitted to the connection points of the engine with the vehicle body. For damping these vibrations, the vehicle has xe2x80x9cshakersxe2x80x9d, thus mechanical vibration exciting devices which are arranged in the area of at least some connection points of the engine with the vehicle body. When the engine is operated, the shakers are excited as a function of the rotational engine speed at the resonance frequencies in the opposite phase to the vibrations coming from the engine, whereby the transmission of the introduced vibrations is at least partially damped. The corresponding frequencies and their amplitudes for the secondary vibrations are taken from a previously filed data field.
From U.S. Pat. No. 5,434,783, a vehicle is known in the case of which the sound effects audible within a passenger compartment are influenced by sound waves. In addition to normal loudspeakers, a piezoelement is also used here which excites the vehicle body at least in an area to carry out vibrations and thereby influences it to emit sound waves; that is, the piezoelement acts like the coil of a loudspeaker, while the vehicle body represents the vibrating membrane. By means of the known method and the known system, an improvement of the subjective sensation is achieved within the occupant compartment.
A further development of the above approach for influencing the subjectively perceived driving sensation is known from German Patent Document DE 195 31 402 A1. According to this document, as a function of a parameter and in this case particularly of the rotational engine speed and/or of the velocity, not only the airborne sound but also the structure-borne sound perceived by means of the body and vibrations are influenced. For this purpose, depending on the extent of the parameter, certain data are read out of a data field and are converted by means of vibration exciting devices, in secondary vibrations which among other things are also perceived on the structure. By means of this measure, in conjunction with the influencing of the acoustically perceived airborne sound, positive as well as negative interferences of the artificial secondary vibrations can be generated with the primary vibrations which form on the vehicle side when the vehicle is operated. As desired, the interferences can reduce the perceived impression or simulate a certain impression, for example, a shifting in the case of a vehicle equipped with an infinitely variable speed transmission.
However, the above-mentioned measures require considerable expenditures. Furthermore, they still require the use of weight-increasing sound-absorbing mats made of a sound-absorbing material.
It is an object of the invention to develop a method and a system by means of which an influencing of noises can be carried out in a novel manner, which noises come from objects which have at least two at least indirectly mutually adjoining and mutually connected components.
According to the invention, this object is achieved by providing a method for influencing at least one of structure-borne sound conductions and noise radiations of objects which have at least two at least indirectly mutually adjoining and mutually connected components, a spacer body being arranged proximate an at least indirectly mutually adjoining area, wherein said spacer body has a controllably influenceable geometry, and wherein the components connected with one another by way of the spacer body are dimensioned with different acoustic impedances with respect to the conduction of the structure-borne sound.
According to the invention, this object is achieved by providing a system for influencing at least one of structure-borne sound conductions and noise radiations of objects which have at least two at least indirectly mutually adjoining and mutually connected components, a spacer body being arranged proximate an at least indirectly mutually adjoining area, wherein the spacer body has a controllably influenceable geometry, and wherein the components which are mutually connected by way of the spacer body have a different acoustic impedance with respect to the conduction of the structure-borne sound.
As the result of the arrangement of spacer bodies, preferably piezoelements arranged in active seals which, at least in areas, can be influenced in a controlled manner in their geometry, the transmission function for vibrations between the individual components of the object can be changed in a simple manner. This is a special advantage particularly in the claimed inventive context by means of the different acoustic impedances of the concerned components. In this combination, the one, acoustically hard component acts as a supporting body for the second, acoustically softer component; that is, the hard component virtually forms a fixing point for the acoustically softer component which can therefore easily and at low-energy be excited to carry out vibrations.
This becomes particularly favorable starting at an impedance ratio of the two components with respect to one another which is lower than 1:2, preferably lower than 1:5 and particularly preferably lower than 1:10.
Expediently, these spacer bodies are additionally also arranged in the area of a high and/or of the maximum mode density of the structure-borne sound, particularly in a joint or in a flange or a partition line between the two components.
In particular, the invention can be used for reducing noise inside an enclosed space. In the same manner, it is possible to influence in a preferably minimizing manner the sounds transmitted to the outside.
The invention is particularly advantageous in the construction and/or of the, in particular, wheel-side fastening of panels, of casing plates, of window panes, of covering parts, particularly of metal body sheets of a vehicle or of an airplane. Furthermore, this also applies to the construction and fastening of, for example, an oil pan on a crankcase, a cylinder block of an engine, an engine mount of an engine or of an engine bearing of an engine mount since, as the result of the invention, a complicated ribbing-out of components which increases the acoustic impedance and thus mass can at least partially be eliminated.
On the whole, this, among other things, reduces costs, which is the result of a simplification of the demands on construction, of a simplified component geometry, which saves casting expenses, etc., as well as of a possible reduction of sound-absorbing measures, by means of, for example, sound-absorbing mats, and the like.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.